All content from Intratec's Chemical Process Library was produced based on reports published by Intratec. To learn more about Ethanol production processes presented below and others examined in Intratec reports, click here.

Ethanol Manufacture from Sugarcane

Ethanol is a widely used commodity chemical with several applications, including use as a solvent and as a gasoline blendstock in the fuel market. Globally, the major portion of ethanol production is based on the fermentation of sugars from crop feedstocks, such as sugarcane, corn, cellulosic material and others. World fuel ethanol production is about 85 billion liters annually, with 60% resulting from corn ethanol production in the U.S., and another 25% from sugarcane ethanol production in Brazil. In view of current environmental issues, including greenhouse gas emissions, fermentation-based ethanol is considered an alternative to fossil fuels since it originates from renewable resources.

Technology Description

Ethanol from sugarcane is traditionally produced by yeast fermentation of sugarcane molasses. Commonly, raw sugar is obtained as a co-product, through crystallization of sugarcane raw juice. The major process steps in sugarcane ethanol production are as follows:

Milling

Sugarcane is delivered from the field to the factory, where it is weighed, cut and shredded before being conducted to the mills, where the raw cane juice is extracted. Sugarcane bagasse is obtained as a residue, and it is burned to generate steam and electricity to supply process demands.

Juice Treatment

The raw cane juice is clarified by treatment with phosphate and lime leading to mud formation, which is separated in a clarifier. The clarifi ed juice is then concentrated under vacuum in a multiple-effect evaporator, forming a sugar syrup.

Sugar Crystallization

Sugar crystallization is accomplished in two vacuum calandrias, where water is evaporated from the syrup and crystallization is induced by the addition of a seeding solution. This process forms a massecuite, a mixture of liquor and sugar crystals. Next, crystallization is completed by cooling in a crystallizer. The raw sugar is centrifuged, dried and sent to storage. In a third calandria-crystallizer set, a massecuite is formed that will become the seeding solution to be used at crystallization, and also the molasses for subsequent fermentation.

Fermentation

The sugars contained in the molasses ...

Economic Performance

Ethanol Manufacture from Woodchips

Ethanol is widely produced by fermentation of sugars from agriculture feedstocks, such as corn and sugarcane. In order to meet growing energy requirements, several lines of research have focused on cellulosic ethanol production, where some type of lignocellulosic biomass, such as woodchips, sugarcane bagasse, corn stover and others, serve as the feedstock for the process.

Use of these raw materials is justified by their low cost, ready availability and status as generally unused residues. Also, such waste biomass feedstocks do not interfere or compete with the production of food from crop feedstocks.

Technology Description

The production process for ethanol from woodchips shown in the simplified flowsheet is similar to the Green Power+ process described in the U.S. patent published by American Process Inc. (Atlanta, Ga.; www.americanprocess.com; U.S. Patent 195,468; 2011). The major process steps are described in the diagram.

Pretreatment

Wood chips are pumped with hot water into the pretreatment reactor, where hemicelluloses are separated from lignin and cellulose. The treated mixture is washed with recycled filtrate. The hemicellulose extract is sent to the first evaporation step, where water is evaporated. Lignin and cellulose are burned to generate steam and electricity to supply plant demands.

Hydrolysis

The hemicelluloses undergo acid hydrolysis ...

Economic Performance

Ethanol Manufacture from the Direct Gasification of Biomass

Increasing global demand for energy and a drive to develop renewable energy sources have focused research and development attention on biomass (including wood, agricultural residues and municipal wastes) as a source of energy and products. Biomass can be converted into bioenergy via biochemical and thermochemical means. In biochemical routes, the biomass is converted into liquid or gaseous fuels by fermentation or anaerobic digestion. In thermochemical conversion, biomass is converted into gases via a number of methods, and the gases are then either used directly or synthesized into the desired chemicals. Thermochemical technologies include combustion, gasification and pyrolysis. This column describes a gasification process to produce ethanol.

Technology Description

In the process of producing ethanol via direct gasification, biomass is converted into synthesis gas (syngas) by partial oxidation and the resulting stream of gases is partially burned to produce heat for the process and partially reacted to produce liquid alcohols. The process can be divided into the following areas: feedstock handling and gasification, gas cleanup and conditioning, alcohol synthesis and alcohol separation.

Feedstock Handling and Gasification

The biomass is dried with fluegas from the fuel combustor in the biomass drier. The dried biomass is fed into the oxygen-blown direct gasifier with steam and high-pressure oxygen from an air-separation unit.

In the presence of steam and oxygen at high temperature, biomass decomposes into syngas — a mixture of mostly H2 and CO, with CH4, CO2, light hydrocarbons and water — and tar, ash and char. The combustion of a portion of the biomass supplies the heat for the endothermic reactions. A cyclone is used at the exit of the gasifier to remove residual solids from the syngas.

Gas Cleanup and Conditioning

Syngas from the gasifier is sent to the fluidized-bed tar ...

Economic Performance

Ethanol Manufacture from Lignocellulosic Biomass

Pressing global issues, such as climate change and declining energy security, have led to an increasing interest in the use of renewable feedstocks for fuel production. These feedstocks include lignocellulosic materials, such as waste biomass from the agriculture and forest industries.

Ethanol is commonly produced by fermentation of sugars from agricultural feedstock — mostly corn and sugarcane. Several processes to produce ethanol by fermenting lignocellulosic materials have been developed. Two such processes have been introduced by American Process Inc. (Atlanta, Ga.; www.americanprocess.com), one of which is discussed below.

Technology Description

The process for cellulosic ethanol production depicted in the simplified process diagram below is similar to the AVAP process described in the World Intellectual Property Organization (Geneva, Switzerland; www.wipo.int) patent published by American Process Inc. (W.O. Patent 2011/044378A1).

Pretreatment

The biomass is heated with a solution of SO2, ethanol and water and then fractionated into its three lignocellulosic components: hemicellulose, cellulose and lignin. Hemicellulose and lignin are partially dissolved, while cellulose remains insoluble. Cellulose is washed and the filtrate is sent to the stripping column, where SO2 and ethanol are recovered in the overhead stream, which is condensed in an evaporator and sent to a make-up vessel. The column bottoms material is concentrated in the evaporator, generating vapor that is compressed and used as steam supply for the evaporator and for the column’s reboiler.